Momentum exchange between the atmosphere and the ocean under the strong-wind conditions
Studies and parametrization of the momentum exchange processes in the boundary layers of the atmosphere and ocean is an important problem from the viewpoing of weather and climate prediction models development . The main parameter, which characterizes this process is the aerodynamic drag coefficient CD. The effect of saturation of CD in the case of an exceeded threshold value of the equivalent wind velocity (velocity at a height of 10 m, U10N) was confirmed in the process of laboratory modeling of wind-wave interaction in IAP RAS HSWWF in a wide range of wind speeds (up to hurricane values). The threshold value ranges from 25 to 30 m/s, which agrees well with the results of the laboratory experiment and the field data obtained earlier. Comparison of this result with parallel measturements of the surface waves, which were performed for the first time, showed that the slope of the dominant waves is saturated at the same time, at the same velocity threshold accompanied by the start of wave breaking. The experimental results agree well with the calculations performed within the framework of the quasilinear model of a turbulent boundary layer with allowance for the contribution of the short-wave fraction of surface perturbations. This research was supported by Project No. 11.G34.31.0048 of the RF Government's Megagrant Program.
Troitskaya Yu. I., Sergeev D. A., Kandaurov A. A., Baidakov G. A., Vdovin M. A., and Kazakov V. I. Laboratory and theoretical modeling of air-sea momentum transfer under severe wind conditions // J. Geophys. Res., 2012, V. 117, P. C00J21(1–13)